Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

018
FXUS63 KLOT 180611
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
111 AM CDT Wed Mar 18 2026

.KEY MESSAGES...

- Untreated surfaces may be slippery this morning owing to a
  coating of snow.

- Another clipper system may deliver rain showers Wednesday
  night into Thursday morning.

- Temperatures will warm toward the 60s to locally lower 70s
  Friday and Saturday. A cold front will move through the area
  at some point Saturday night or Sunday.

&&

.DISCUSSION...
Issued at 108 AM CDT Wed Mar 18 2026

"Streaky" bands of snow continue to stream over the area within
the warm-air advection regime of a low-amplitude wave
propagating toward the Ohio River Valley. Pockets of dry low-
level air have been chewing up a majority of snowflakes on their
journey to the ground thus far. With that said, the expectation
is for snow to eventually make it down through the early
morning hours. Fairly modest forcing (peak lift of only minus 3
to 4 ubar/sec) will limit overall snow accumulations with this
system, favoring generally a coating where snow is most
persistent.

Snow should end from northwest to southeast toward and
especially by daybreak. An initially cloudy start to the day
will transition toward partly cloudy (to even mostly sunny)
skies. Highs today should top off in the upper 30s near the
Wisconsin state line to around 50 near US-24.

Clouds will increase tonight as another low-amplitude waves
approaches the Great Lakes. Another bout of low-level warm air
advection may act to counteract diurnal cooling (if not
encourage temperatures to warm a degree or two though the
night), with lows expected to settle in the lower 30s. The next
wave will be accompanied by a pocket of modestly steep mid-level
lapse rates (near 7K/km), which should allow for scattered
showers to develop through the early morning hours of Thursday.
Coverage of showers is currently favored north of I-80, though
any adjustment in the track of the wave would be subject
adjustments to the area of highest shower coverage.

At this point, it appears shower coverage should wane by
daybreak Thursday, setting the stage for clearing skies and a
warm early spring day. With 850mb temperatures expected to
settle near +4 to +5C, afternoon highs on Thursday will have
the potential to shoot into the upper 50s to lower 60s. With a
weak pressure gradient in place and lake Michigan temperatures
in the upper 30s, a strong lake breeze should develop by early
afternoon and drive lakeside temperatures downward back into the
40s. (It is the season for "cooler by the lake," after all).

This weekend, the monster upper-level ridge across the
southwestern United States will shift eastward, leading to
quasi-zonal flow across the Great Lakes. Interestingly, ensemble
model guidance is somewhat split with how fast the low-level
thermal ridge will expands eastward, with the GFS/GEFS camp
decidedly slower than the ECMWF/EPS camp. Such differences have
fairly large consequences on the temperature forecast, including
the arrival time of a cold front at some point this weekend associated
with an upper- level wave propagating within the zonal flow
aloft. Regardless, with 850mb temperatures poised to rocket
toward +15C, current thinking is at least one day of the weekend
(Saturday or Sunday) will have a shot of having high
temperatures in the upper 60s to lower 70s before a cold front
brings high temperatures back into the 40s and 50s to start next
week.

Borchardt

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1254 AM CDT Wed Mar 18 2026

Key Messages:

- Snow will continue through around sunrise, resulting in
  IFR/MVFR visibilities.

- A chance for rain is forecasted towards the end of the TAF
  period.


Snow has spread over the terminals at the start of the TAF
period and is expected to continue through the overnight hours
before ending from northwest to southeast closer to sunrise.
IFR visibilities will occur during the periods of steadier
snowfall, and MVFR ceilings will be observed as well. Total
snow accumulations are still expected to end up being around 1"
or a little less. Still couldn`t completely rule out a brief
period of freezing drizzle right as the snow comes to an end,
but the most likely outcome (~90% chance) is that no freezing
drizzle occurs.

Another chance for precipitation will come towards the end of
the current TAF period as the next upper-level disturbance dives
into the region. Thermal profiles should have warmed up enough
by this point for most or all of this precipitation to come down
as rain, but it is possible that air temperatures may still be
cold enough for this rain to freeze on colder surfaces. The
track that the bulk of this precipitation will take is still
somewhat uncertain, with about a 35-45% chance at this time for
it to occur at ORD and MDW prior to the end of the 30-hour TAF
period there. Thus, have elected to highlight this
precipitation potential in a PROB30 group for starters.

Southerly winds with gusts to 20-25 kts will gradually diminish
over the course of the daytime today while turning
southwesterly before becoming light this evening into Thursday
morning.

Ogorek

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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